Documenting the Performance of Retrofitted URM Buildings

Several EERI Team members have been collaborating with University of Canterbury coordinator on this subject Prof. Rakesh Dhakal to try to capture the ephemeral effects of the earthquake on all known retrofitted URM buildings in the Canterbury Province that were shaken with significant motions in the February 22 aftershock. In that process dozens of additional buildings were added to the list of roughly 60 buildings that appeared to have some seismic improvements visible from the exterior, or that, by word of mouth, were reportedly partially or systematically (completely) retrofitted at some time in their life. The range of partial retrofits may be from the 1930’s to the present, and the range of relatively complete retrofits that attempt to address most modes of response likely range from the 1960’s to the present. With the collaboration of EEFIT team members, and now a group of University of Auckland researchers that have just obtained more financial support for this effort, it is likely that we have captured images of each elevation, closeups of relevant details or substantial cracking or failure patterns, and where access to the interiors of retrofitted URMs were possible images of the interior improvements and a much better sense of the major elements of the lateral force resisting system were documented.

The University of Auckland researchers whose contact is Dmytro Dizhur is also collecting samples of performance documentation forms used by the U.S. including SEAOC’s Earthquake Performance Evaluation Program and Italy’s forms. They plan to generate their own forms to enable more consistency in the documentation, and future search and retrieval.

The EERI Team plans to geotag, map, caption and share its images with these efforts and begin to articulate preliminary trends and other issues that are both relevant and beneficial to retrofit practice in New Zealand, Canada, and the U.S. shortly.

On the whole, retrofits resulted in distinct improvements in performance compared to nearby non-retrofitted URM buildings. However, several buildings exhibited responses in this aftershock that could result in significant changes to how retrofits are proportioned for design purposes and installed to ensure construction quality and overall more reliable performance.

This work is generating a rather extraordinary amount of information through international collaboration, and it should help create a mutual understanding about the performance of a wide variety of retrofit approaches.